1
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Bailey JJ, Wuest M, Bojovic T, Kronemann T, Wängler C, Wängler B, Wuest F, Schirrmacher R. On the Viability of Tadalafil-Based 18F-Radiotracers for In Vivo Phosphodiesterase 5 (PDE5) PET Imaging. ACS OMEGA 2021; 6:21741-21754. [PMID: 34471776 PMCID: PMC8388084 DOI: 10.1021/acsomega.1c03315] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 07/29/2021] [Indexed: 06/13/2023]
Abstract
Phosphodiesterase 5 (PDE5) is a clinically relevant biomarker and therapeutic target for many human pathologies, yet a noninvasive agent for the assessment of PDE5 expression has yet to be realized. Such agents would improve our understanding of the nitric oxide (NO)/cyclic guanosine 3',5'-monophosphate (cGMP)/PDE5 pathway in human pathologies and potentially lead to novel uses of PDE5 inhibitors to manage lung conditions like SARS-CoV-2-mediated pulmonary inflammatory responses. In this study, efforts were made to produce an 18F-labeled analogue of the PDE5 inhibitor tadalafil to visualize PDE5 expression in vivo with positron emission tomography (PET). However, during the late-stage fluorination step, quantitative epimerization of the tadalafil C12a stereocenter occurred, yielding a less active epi-isomer. In vivo dynamic microPET images in mice revealed that the epimerized radiotracer, [18F]epi-18, rapidly accumulated in the liver with negligible uptake in tissues of known PDE5 expression.
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Affiliation(s)
- Justin J. Bailey
- Department
of Oncology, Cross Cancer Institute, University
of Alberta, Edmonton, Alberta T6G 1Z2, Canada
| | - Melinda Wuest
- Department
of Oncology, Cross Cancer Institute, University
of Alberta, Edmonton, Alberta T6G 1Z2, Canada
| | - Tamara Bojovic
- Department
of Oncology, Cross Cancer Institute, University
of Alberta, Edmonton, Alberta T6G 1Z2, Canada
| | - Travis Kronemann
- Department
of Oncology, Cross Cancer Institute, University
of Alberta, Edmonton, Alberta T6G 1Z2, Canada
| | - Carmen Wängler
- Biomedical Chemistry, Department
of Clinical Radiology and Nuclear
Medicine and Molecular Imaging and Radiochemistry, Department of Clinical Radiology
and Nuclear Medicine, Medical Faculty Mannheim
of Heidelberg University, Theodor-Kutzer-Ufer 1-3, Mannheim 68167, Germany
| | - Björn Wängler
- Biomedical Chemistry, Department
of Clinical Radiology and Nuclear
Medicine and Molecular Imaging and Radiochemistry, Department of Clinical Radiology
and Nuclear Medicine, Medical Faculty Mannheim
of Heidelberg University, Theodor-Kutzer-Ufer 1-3, Mannheim 68167, Germany
| | - Frank Wuest
- Department
of Oncology, Cross Cancer Institute, University
of Alberta, Edmonton, Alberta T6G 1Z2, Canada
| | - Ralf Schirrmacher
- Department
of Oncology, Cross Cancer Institute, University
of Alberta, Edmonton, Alberta T6G 1Z2, Canada
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2
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Sun J, Xiao Z, Haider A, Gebhard C, Xu H, Luo HB, Zhang HT, Josephson L, Wang L, Liang SH. Advances in Cyclic Nucleotide Phosphodiesterase-Targeted PET Imaging and Drug Discovery. J Med Chem 2021; 64:7083-7109. [PMID: 34042442 DOI: 10.1021/acs.jmedchem.1c00115] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cyclic nucleotide phosphodiesterases (PDEs) control the intracellular concentrations of cAMP and cGMP in virtually all mammalian cells. Accordingly, the PDE family regulates a myriad of physiological functions, including cell proliferation, differentiation and apoptosis, gene expression, central nervous system function, and muscle contraction. Along this line, dysfunction of PDEs has been implicated in neurodegenerative disorders, coronary artery diseases, chronic obstructive pulmonary disease, and cancer development. To date, 11 PDE families have been identified; however, their distinct roles in the various pathologies are largely unexplored and subject to contemporary research efforts. Indeed, there is growing interest for the development of isoform-selective PDE inhibitors as potential therapeutic agents. Similarly, the evolving knowledge on the various PDE isoforms has channeled the identification of new PET probes, allowing isoform-selective imaging. This review highlights recent advances in PDE-targeted PET tracer development, thereby focusing on efforts to assess disease-related PDE pathophysiology and to support isoform-selective drug discovery.
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Affiliation(s)
- Jiyun Sun
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
| | - Zhiwei Xiao
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
| | - Ahmed Haider
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
| | - Catherine Gebhard
- Department of Nuclear Medicine, University Hospital Zurich, Raemistrasse 100, Zurich 8006, Switzerland.,Center for Molecular Cardiology, University of Zurich, Wagistrasse 12, Schlieren 8952, Switzerland
| | - Hao Xu
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, 613 West Huangpu Road, Tianhe District, Guangzhou 510630, China
| | - Hai-Bin Luo
- School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Han-Ting Zhang
- Departments of Neuroscience, Behavioral Medicine & Psychiatry, and Physiology & Pharmacology, the Rockefeller Neuroscience Institute, West Virginia University Health Sciences Center, Morgantown, West Virginia 26506, United States
| | - Lee Josephson
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
| | - Lu Wang
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States.,Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, 613 West Huangpu Road, Tianhe District, Guangzhou 510630, China
| | - Steven H Liang
- Department of Radiology, Division of Nuclear Medicine and Molecular Imaging Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States
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3
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Xu Z, Jia L, Liu W, Li W, Song Y, Zheng QH. Radiosynthesis of a carbon-11 labeled PDE5 inhibitor [ 11C]TPN171 as a new potential PET heart imaging agent. Appl Radiat Isot 2020; 162:109190. [PMID: 32501230 DOI: 10.1016/j.apradiso.2020.109190] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 03/25/2020] [Accepted: 04/20/2020] [Indexed: 12/28/2022]
Abstract
To develop PET tracers for imaging of heart disease, a new carbon-11 labeled potent and selective PDE5 inhibitor [11C]TPN171 ([11C]9) has been synthesized. The reference standard TPN171 (9) and its corresponding precursor desmethyl-TPN171 (11) were synthesized from methyl 3-oxovalerate and 2-hydroxybenzonitrile in 9 and 10 steps with 31% and 25% overall chemical yield, respectively. The radiotracer [11C]TPN171 was prepared from desmethyl-TPN171 with [11C]CH3OTf through N-11C-methylation and isolated by HPLC purification followed by SPE formulation in 45-55% radiochemical yield, based on [11C]CO2 and decay corrected to EOB. The radiochemical purity was >99%, and the molar activity (Am) at EOB was in a range of 370-740 GBq/μmol.
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Affiliation(s)
- Zhidong Xu
- College of Chemical & Pharmaceutical Engineering, Key Laboratory of Molecular Chemistry for Medicine of Hebei Province, Hebei University of Science & Technology, Shijiazhuang, Hebei, 050018, China; Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, College of Chemistry & Environmental Science, Hebei University, Baoding, Hebei, 071002, China
| | - Limeng Jia
- Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, College of Chemistry & Environmental Science, Hebei University, Baoding, Hebei, 071002, China
| | - Wenqing Liu
- College of Chemical & Pharmaceutical Engineering, Key Laboratory of Molecular Chemistry for Medicine of Hebei Province, Hebei University of Science & Technology, Shijiazhuang, Hebei, 050018, China
| | - Wei Li
- Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, College of Chemistry & Environmental Science, Hebei University, Baoding, Hebei, 071002, China
| | - Ying Song
- Department of Chemical and Environmental Engineering, Hebei College of Industry & Technology, Shijiazhuang, Hebei, 050000, China.
| | - Qi-Huang Zheng
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, 1345 West, 16th Street, Room 208, Indianapolis, IN, 46202, USA.
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4
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Wenzel B, Liu J, Dukic-Stefanovic S, Deuther-Conrad W, Teodoro R, Ludwig FA, Chezal JM, Moreau E, Brust P, Maisonial-Besset A. Targeting cyclic nucleotide phosphodiesterase 5 (PDE5) in brain: Toward the development of a PET radioligand labeled with fluorine-18. Bioorg Chem 2019; 86:346-362. [PMID: 30753989 DOI: 10.1016/j.bioorg.2019.01.037] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 01/08/2019] [Accepted: 01/21/2019] [Indexed: 01/15/2023]
Abstract
With the aim to develop a specific radioligand for imaging the cyclic nucleotide phosphodiesterase 5 (PDE5) in brain by positron emission tomography (PET), seven new fluorinated inhibitors (3-9) were synthesized on the basis of a quinoline core. The inhibitory activity for PDE5 together with a panel of other PDEs was determined in vitro and two derivatives were selected for IC50 value determination. The most promising compound 7 (IC50 = 5.92 nM for PDE5A), containing a 3-fluoroazetidine moiety, was further radiolabeled by aliphatic nucleophilic substitution of two different leaving groups (nosylate and tosylate) using [18F]fluoride. The use of the nosylate precursor and tetra-n-butyl ammonium [18F]fluoride ([18F]TBAF) in 3-methyl-3-pentanol combined with the addition of a small amount of water proved to be the best radiolabeling conditions achieving a RCY of 4.9 ± 1.5% in an automated procedure. Preliminary biological investigations in vitro and in vivo were performed to characterize this new PDE5 radioligand. Metabolism studies of [18F]7 in mice revealed a fast metabolic degradation with the formation of radiometabolites which have been detected in the brain.
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Affiliation(s)
- Barbara Wenzel
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Department of Neuroradiopharmaceuticals, Leipzig, Germany.
| | - Jianrong Liu
- UMR 1240 INSERM IMOST, Université Clermont-Auvergne, Clermont-Ferrand, France
| | - Sladjana Dukic-Stefanovic
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Winnie Deuther-Conrad
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Rodrigo Teodoro
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Friedrich-Alexander Ludwig
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Department of Neuroradiopharmaceuticals, Leipzig, Germany
| | - Jean-Michel Chezal
- UMR 1240 INSERM IMOST, Université Clermont-Auvergne, Clermont-Ferrand, France
| | - Emmanuel Moreau
- UMR 1240 INSERM IMOST, Université Clermont-Auvergne, Clermont-Ferrand, France
| | - Peter Brust
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Department of Neuroradiopharmaceuticals, Leipzig, Germany
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5
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Affiliation(s)
- Moustafa A. Gouda
- Department of Chemistry, Faculty of Science and Arts, Taibah University, Ulla, Kingdom of Saudi Arabia
- Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, Egypt
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6
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Liu J, Maisonial-Besset A, Wenzel B, Canitrot D, Baufond A, Chezal JM, Brust P, Moreau E. Synthesis and in vitro evaluation of new fluorinated quinoline derivatives with high affinity for PDE5: Towards the development of new PET neuroimaging probes. Eur J Med Chem 2017; 136:548-560. [PMID: 28544981 DOI: 10.1016/j.ejmech.2017.03.091] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 03/03/2017] [Accepted: 03/26/2017] [Indexed: 12/20/2022]
Abstract
The increasing incidence of Alzheimer's disease (AD) worldwide is a major public health problem. Current treatments provide only palliative solutions with significant side effects. Therefore, new efficient treatment options and novel early diagnosis tools are urgently needed. Recently, strong pre-clinical evidences suggested that phosphodiesterase 5 (PDE5) may be clinically relevant both as biomarker and drug-target in AD. In this study, we intended to develop a new radiofluorinated tracer for the visualisation of PDE5 in brain using PET imaging. Based on currently known PDE5 inhibitors, a series of novel fluorinated compounds bearing a quinoline core have been synthesised via multi-steps reaction pathways. Their affinity for PDE5 and selectivity over other PDE families have been investigated. According to the data collected from this in vitro screening, fluorinated derivatives 24a, b bearing a fluoroethoxy group at the C-3 position of the quinoline core appeared to be the most promising structures and will be further radiolabelled with fluorine-18 for in vitro and in vivo evaluations as PET radiotracer for neuroimaging of PDE5.
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Affiliation(s)
- Jianrong Liu
- Univ. Clermont Auvergne, INSERM, UMR 1240, IMOST, F-63005 Clermont-Ferrand, France.
| | | | - Barbara Wenzel
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Dept. of Neuroradiopharmaceuticals, Permoserstrasse 15, 04318 Leipzig, Germany.
| | - Damien Canitrot
- Univ. Clermont Auvergne, INSERM, UMR 1240, IMOST, F-63005 Clermont-Ferrand, France.
| | - Ariane Baufond
- Univ. Clermont Auvergne, INSERM, UMR 1240, IMOST, F-63005 Clermont-Ferrand, France.
| | - Jean-Michel Chezal
- Univ. Clermont Auvergne, INSERM, UMR 1240, IMOST, F-63005 Clermont-Ferrand, France.
| | - Peter Brust
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Dept. of Neuroradiopharmaceuticals, Permoserstrasse 15, 04318 Leipzig, Germany.
| | - Emmanuel Moreau
- Univ. Clermont Auvergne, INSERM, UMR 1240, IMOST, F-63005 Clermont-Ferrand, France.
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7
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Chekol R, Gheysens O, Ahamed M, Cleynhens J, Pokreisz P, Vanhoof G, Janssens S, Verbruggen A, Bormans G. Carbon-11 and Fluorine-18 Radiolabeled Pyridopyrazinone Derivatives for Positron Emission Tomography (PET) Imaging of Phosphodiesterase-5 (PDE5). J Med Chem 2016; 60:486-496. [PMID: 28009175 DOI: 10.1021/acs.jmedchem.6b01666] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The cyclic guanosine monophosphate (cGMP) specific phosphodiesterase type 5 (PDE5) plays an important role in various pathologies including pulmonary arterial hypertension and cardiomyopathy. PDE5 represents an important therapeutic and/or prognostic target, but noninvasive assessment of PDE5 expression is lacking. The purpose of this study was to develop and evaluate pyridopyrazinone derivatives labeled with carbon-11 or fluorine-18 as PDE5-specific PET tracers. In biodistribution studies, highest PDE5-specific retention was observed for [11C]-12 and [18F]-17 in the lungs of wild-type mice and in the myocardium of transgenic mice with cardiomyocyte-specific PDE5 overexpression at 30 min postinjection. In vivo dynamic microPET images in rats revealed that both tracers crossed the blood-brain barrier but brain retention was not PDE5-specific. Both [11C]-12 and [18F]-17 showed specific binding to PDE5 in myocardium of transgenic mice; however [18F]-17 showed significantly higher PDE5-specific inhibitable binding than [11C]-12.
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Affiliation(s)
- Rufael Chekol
- Laboratory of Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven , BE-3000 Leuven, Belgium
| | - Olivier Gheysens
- Department of Imaging and Pathology, KU Leuven , and Nuclear Medicine, UZ Leuven, BE-300 Leuven Belgium
| | - Muneer Ahamed
- Laboratory of Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven , BE-3000 Leuven, Belgium
| | - Jan Cleynhens
- Laboratory of Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven , BE-3000 Leuven, Belgium
| | - Peter Pokreisz
- Department of Cardiovascular Sciences, UZ Leuven, KU Leuven , 3000 Leuven, Belgium
| | - Greet Vanhoof
- Discovery Sciences, Janssen Pharmaceutica, R&D , B-2340 Beerse, Belgium
| | - Stefan Janssens
- Department of Cardiovascular Sciences, UZ Leuven, KU Leuven , 3000 Leuven, Belgium
| | - Alfons Verbruggen
- Laboratory of Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven , BE-3000 Leuven, Belgium
| | - Guy Bormans
- Laboratory of Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven , BE-3000 Leuven, Belgium
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8
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Cheng G, Werner TJ, Newberg A, Alavi A. Failed PET Application Attempts in the Past, Can We Avoid Them in the Future? Mol Imaging Biol 2016; 18:797-802. [DOI: 10.1007/s11307-016-1017-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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9
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Cumming P. A business of some heat: molecular imaging of phosphodiesterase 5. J Neurochem 2016; 136:220-1. [PMID: 26990291 DOI: 10.1111/jnc.13453] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 11/23/2015] [Accepted: 11/26/2015] [Indexed: 12/14/2022]
Affiliation(s)
- Paul Cumming
- Department of Neuropsychiatry and Psychosomatic Medicine, Oslo University Hospital, Oslo, Norway.,School of Psychology and Counselling, Queensland University of Technology, and QIMR Berghofer Medical Research Institute, Brisbane, Australia
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10
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Gómez-Vallejo V, Ugarte A, García-Barroso C, Cuadrado-Tejedor M, Szczupak B, Dopeso-Reyes IG, Lanciego JL, García-Osta A, Llop J, Oyarzabal J, Franco R. Pharmacokinetic investigation of sildenafil using positron emission tomography and determination of its effect on cerebrospinal fluid cGMP levels. J Neurochem 2016; 136:403-15. [PMID: 26641206 DOI: 10.1111/jnc.13454] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 11/17/2015] [Accepted: 11/20/2015] [Indexed: 11/29/2022]
Abstract
Sildenafil (Viagra) is a selective inhibitor of phosphodiesterase type 5 (PDE5), which degrades cyclic guanosine monophosphate to the linear nucleotide. Sildenafil is acutely used in erectile dysfunction and chronically in pulmonary hypertension. Evidence in the last decade shows that sildenafil may have potential as a therapeutic option for Alzheimer's disease or other neurodegenerative disorders. The purpose of this work was to explore whether sildenafil crosses the blood-brain barrier. Pharmacokinetic properties of sildenafil in rodents were investigated using (11) C-radiolabeling followed by in vivo positron emission tomography (PET) and ex vivo tissue dissection and gamma counting. PET results in rats suggest penetration into the central nervous system. Ex vivo data in perfused animals suggest that trapping of [(11) C]sildenafil within the cerebral vascular endothelium limits accumulation in the central nervous system parenchyma. Peroral sildenafil administration to Macaca fascicularis and subsequent chemical analysis of plasma and cerebrospinal fluid (CSF) using liquid chromatography coupled with tandem mass spectrometry showed that drug content in the CSF was high enough to achieve PDE5 inhibition, which was also demonstrated by the significant increases in CSF cyclic guanosine monophosphate levels. Central actions of sildenafil include both relaxation of the cerebral vasculature and inhibition of PDE5 in neurons and glia. This central action of sildenafil may underlie its efficacy in neuroprotection models, and may justify the continued search for a PDE5 ligand suitable for PET imaging. Sildenafil interacts with phosphodiesterase type 5 (PDE5) expressed in the endothelium and/or smooth muscle cells of brain vessels and also crosses the blood-brain barrier to interact with PDE5 expressed in brain cells. At therapeutic doses, the concentration of sildenafil in the cerebrospinal fluid (CSF) is high enough to inhibit PDE5 in the neural cells (neurons and glia). In turn, the concentration of cGMP likely increases in parenchymal cells and, as shown in this report, in the CSF. Read the Editorial Highlight for this article on page 220. Cover Image for this issue: doi: 10.1111/jnc.13302.
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Affiliation(s)
| | - Ana Ugarte
- Small Molecule Discovery Platform, Molecular Therapeutics Program, Centre for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain
| | - Carolina García-Barroso
- Neurobiology of Alzheimer's disease, Neurosciences Division, Centre for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain
| | - Mar Cuadrado-Tejedor
- Neurobiology of Alzheimer's disease, Neurosciences Division, Centre for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain.,Anatomy Department, School of Medicine, University of Navarra, Pamplona, Spain
| | | | - Iria G Dopeso-Reyes
- Neurosciences Division, Centre for Applied Medical Research, CIMA, University of Navarra, Pamplona, Spain.,Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CIBERNED), Pamplona, Spain.,Instituto de Investigaciones Sanitarias de Navarra (IdiSNA), Pamplona, Spain
| | - José L Lanciego
- Neurosciences Division, Centre for Applied Medical Research, CIMA, University of Navarra, Pamplona, Spain.,Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CIBERNED), Pamplona, Spain.,Instituto de Investigaciones Sanitarias de Navarra (IdiSNA), Pamplona, Spain
| | - Ana García-Osta
- Neurobiology of Alzheimer's disease, Neurosciences Division, Centre for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain
| | - Jordi Llop
- Radiochemistry and Nuclear Imaging Group, CIC biomaGUNE, San Sebastian, Spain
| | - Julen Oyarzabal
- Small Molecule Discovery Platform, Molecular Therapeutics Program, Centre for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain
| | - Rafael Franco
- Neurobiology of Alzheimer's disease, Neurosciences Division, Centre for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain
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11
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Novel Radioligands for Cyclic Nucleotide Phosphodiesterase Imaging with Positron Emission Tomography: An Update on Developments Since 2012. Molecules 2016; 21:molecules21050650. [PMID: 27213312 PMCID: PMC6273803 DOI: 10.3390/molecules21050650] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 05/09/2016] [Accepted: 05/10/2016] [Indexed: 12/19/2022] Open
Abstract
Cyclic nucleotide phosphodiesterases (PDEs) are a class of intracellular enzymes that inactivate the secondary messenger molecules, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Thus, PDEs regulate the signaling cascades mediated by these cyclic nucleotides and affect fundamental intracellular processes. Pharmacological inhibition of PDE activity is a promising strategy for treatment of several diseases. However, the role of the different PDEs in related pathologies is not completely clarified yet. PDE-specific radioligands enable non-invasive visualization and quantification of these enzymes by positron emission tomography (PET) in vivo and provide an important translational tool for elucidation of the relationship between altered expression of PDEs and pathophysiological effects as well as (pre-)clinical evaluation of novel PDE inhibitors developed as therapeutics. Herein we present an overview of novel PDE radioligands for PET published since 2012.
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12
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Liu J, Wenzel B, Dukic-Stefanovic S, Teodoro R, Ludwig FA, Deuther-Conrad W, Schröder S, Chezal JM, Moreau E, Brust P, Maisonial-Besset A. Development of a New Radiofluorinated Quinoline Analog for PET Imaging of Phosphodiesterase 5 (PDE5) in Brain. Pharmaceuticals (Basel) 2016; 9:E22. [PMID: 27110797 PMCID: PMC4932540 DOI: 10.3390/ph9020022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 04/12/2016] [Accepted: 04/13/2016] [Indexed: 11/16/2022] Open
Abstract
Phosphodiesterases (PDEs) are enzymes that play a major role in cell signalling by hydrolysing the secondary messengers cyclic adenosine monophosphate (cAMP) and/or cyclic guanosine monophosphate (cGMP) throughout the body and brain. Altered cyclic nucleotide-mediated signalling has been associated with a wide array of disorders, including neurodegenerative disorders. Recently, PDE5 has been shown to be involved in neurodegenerative disorders such as Alzheimer's disease, but its precise role has not been elucidated yet. To visualize and quantify the expression of this enzyme in brain, we developed a radiotracer for specific PET imaging of PDE5. A quinoline-based lead compound has been structurally modified resulting in the fluoroethoxymethyl derivative ICF24027 with high inhibitory activity towards PDE5 (IC50 = 1.86 nM). Radiolabelling with fluorine-18 was performed by a one-step nucleophilic substitution reaction using a tosylate precursor (RCY(EOB) = 12.9% ± 1.8%; RCP > 99%; SA(EOS) = 70-126 GBq/μmol). In vitro autoradiographic studies of [(18)F]ICF24027 on different mouse tissue as well as on porcine brain slices demonstrated a moderate specific binding to PDE5. In vivo studies in mice revealed that [(18)F]ICF24027 was metabolized under formation of brain penetrable radiometabolites making the radiotracer unsuitable for PET imaging of PDE5 in brain.
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Affiliation(s)
- Jianrong Liu
- INSERM-Université d'Auvergne, UMR 990, IMTV, BP 184, F-63005 Clermont-Ferrand Cedex, France.
| | - Barbara Wenzel
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstrasse 15, 04318 Leipzig, Germany.
| | - Sladjana Dukic-Stefanovic
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstrasse 15, 04318 Leipzig, Germany.
| | - Rodrigo Teodoro
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstrasse 15, 04318 Leipzig, Germany.
| | - Friedrich-Alexander Ludwig
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstrasse 15, 04318 Leipzig, Germany.
| | - Winnie Deuther-Conrad
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstrasse 15, 04318 Leipzig, Germany.
| | - Susann Schröder
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstrasse 15, 04318 Leipzig, Germany.
| | - Jean-Michel Chezal
- INSERM-Université d'Auvergne, UMR 990, IMTV, BP 184, F-63005 Clermont-Ferrand Cedex, France.
| | - Emmanuel Moreau
- INSERM-Université d'Auvergne, UMR 990, IMTV, BP 184, F-63005 Clermont-Ferrand Cedex, France.
| | - Peter Brust
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Permoserstrasse 15, 04318 Leipzig, Germany.
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Ohira H, Beanlands RS, Davies RA, Mielniczuk L. The role of nuclear imaging in pulmonary hypertension. J Nucl Cardiol 2015; 22:141-57. [PMID: 25161042 DOI: 10.1007/s12350-014-9960-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 07/17/2014] [Indexed: 12/14/2022]
Abstract
Pulmonary hypertension (PH) is a disease characterized by a chronic elevation of pulmonary artery pressure from various causes. Pulmonary artery hypertension (PAH) is one of subtype which results in premature death often as a result of right ventricular (RV) dysfunction. In spite of the recent progress in novel cardiac imaging techniques and new drugs for PAH, there remain significant unresolved issues including a need for earlier diagnosis, refinement of risk stratification, and monitoring the effects of treatment. Cardiac and pulmonary imaging with transthoracic echocardiography (TTE) with Doppler, magnetic resonance imaging (MRI), and computed tomography (CT) are done routinely in many clinical centers. However, routine and emerging nuclear techniques may have a pivotal role of assessment of the patient with PH, and is currently the subject of significant research. Potential Roles for Nuclear Imaging in the Evaluation of the PH Patient: (1) Evaluation of cardiac structure and function (RNA) (non-nuclear techniques would include TTE, CT, and MRI). (2) Functional imaging. This includes the use of ventilation-perfusion scintigraphy (V/Q scan) to diagnose chronic thromboembolic pulmonary hypertension (CTEPH), 123l-metaiodobenzylguanidine (MIBG) imaging to evaluate the cardiac sympathetic nervous system (non-nuclear techniques include invasive right heart catheterization and TTE). (3) Measurement of RV perfusion (with gated SPECT studies). (4) Evaluation of cardiac and pulmonary metabolism (PET scans). This review article will summarize the pathophysiology, classification, natural history, and diagnostic approach of PH. Current and emerging nuclear techniques will be discussed under the four themes of evaluation of structure, functional imaging, flow, and metabolism. These will be compared to current and emerging nuclear and non-nuclear diagnostic tests in the evaluation and management of patients with PH. We will also discuss research applications exploring new insights into flow and metabolism in the right heart and lung and the application of new radioligands.
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Affiliation(s)
- H Ohira
- Advanced Heart Disease and Pulmonary Hypertension Programs, National Cardiac PET Centre, Division of Cardiology, Department of Medicine, University of Ottawa Heart Institute, 40 Ruskin Street, Room 3409, Ottawa, ON, K1Y 4W7, Canada
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Ahmadi A, Ohira H, Mielniczuk LM. FDG PET Imaging for Identifying Pulmonary Hypertension and Right Heart Failure. Curr Cardiol Rep 2014; 17:555. [DOI: 10.1007/s11886-014-0555-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Chekol R, Gheysens O, Cleynhens J, Pokreisz P, Vanhoof G, Ahamed M, Janssens S, Verbruggen A, Bormans G. Evaluation of PET radioligands for in vivo visualization of phosphodiesterase 5 (PDE5). Nucl Med Biol 2013; 41:155-62. [PMID: 24290227 DOI: 10.1016/j.nucmedbio.2013.10.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 09/23/2013] [Accepted: 10/23/2013] [Indexed: 10/26/2022]
Abstract
INTRODUCTION The cyclic guanosine monophosphate (cGMP) specific phosphodiesterase type 5 (PDE5) is considered to play an important role in various etiologies such as pulmonary arterial hypertension (PAH) and chronic heart failure. This PDE5 modulation represents an important prognostic and/or therapeutic target; however, there is currently no method to non-invasively evaluate the PDE5 expression levels in vivo. METHODS Radiolabeled tracers were prepared by N-alkylation of the corresponding precursors with [(11)C]methyl trifluoromethanesulfonate ([(11)C]CH3OTf) or 2-[(18)F]fluoroethyl trifluoromethanesulfonate ([(18)F]FEtOTf). Biodistribution of radiolabeled tracers was studied in NMRI mice and their specific binding to PDE5 was investigated by comparing their lung retention as the enzyme is abundantly expressed in this organ. RESULTS The overall radiochemical yields ranged between 24% and 60% for labeled radiotracers with radiochemical purity of>99%. The highest retention in the lungs at 30min post injection was observed for vardenafil derivatives [(11)C]-7 and [(18)F]-11 and the retention of the ethoxyethyl pyrazolopyrimidine derivative [(11)C]-37 was moderate. The other investigated compounds [(11)C]-8, [(11)C]-14, [(11)C]-21 and [(11)C]-33 showed lower retention in lungs in agreement with their lower in-vitro affinity for PDE5. CONCLUSION Among the different radiolabeled PDE5 inhibitors evaluated in this study, the vardenafil derivatives [(11)C]-7 and [(18)F]-11 are found to be promising tracers for in vivo visualization of PDE5.
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Affiliation(s)
- Rufael Chekol
- KU Leuven, Laboratory of Radiopharmacy, Leuven, Belgium
| | - Olivier Gheysens
- KU Leuven, Department of Imaging and Pathology, Leuven, Belgium and Nuclear Medicine, UZ Leuven
| | - Jan Cleynhens
- KU Leuven, Laboratory of Radiopharmacy, Leuven, Belgium
| | - Peter Pokreisz
- KU Leuven, Departement of Cardiovascular Sciences, Leuven, Belgium
| | - Greet Vanhoof
- C.R.E.A.Te Translational Sciences, Janssen Pharmaceutica, R&D, Beerse, Belgium
| | - Muneer Ahamed
- KU Leuven, Laboratory of Radiopharmacy, Leuven, Belgium
| | - Stefan Janssens
- KU Leuven, Departement of Cardiovascular Sciences, Leuven, Belgium
| | | | - Guy Bormans
- KU Leuven, Laboratory of Radiopharmacy, Leuven, Belgium.
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Weninger S, De Maeyer JH, Lefebvre RA. Influence of phosphodiesterases and cGMP on cAMP generation and on phosphorylation of phospholamban and troponin I by 5-HT4 receptor activation in porcine left atrium. Naunyn Schmiedebergs Arch Pharmacol 2013; 386:671-84. [PMID: 23549671 DOI: 10.1007/s00210-013-0855-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 03/15/2013] [Indexed: 12/25/2022]
Abstract
Our objective was to investigate the role of phosphodiesterase (PDE)3 and PDE4 and cGMP in the control of cAMP metabolism and of phosphorylation of troponin I (TnI) and phospholamban (PLB) when 5-HT4 receptors are activated in pig left atrium. Electrically paced porcine left atrial muscles, mounted in organ baths, received stimulators of particulate guanylyl cyclase (pGC) or soluble guanylyl cyclase (sGC) and/or specific PDE inhibitors followed by 5-HT or the 5-HT4 receptor agonist prucalopride. Muscles were freeze-clamped at different moments of exposure to measure phosphorylation of the cAMP/protein kinase A targets TnI and PLB by immunoblotting and cAMP levels by enzyme immunoassay. Corresponding with the functional results, 5-HT only transiently increased cAMP content, but caused a less quickly declining phosphorylation of PLB and did not significantly change TnI phosphorylation. Under combined PDE3 and PDE4 inhibition, the 5-HT-induced increase in cAMP levels and PLB phosphorylation was enhanced and sustained, and TnI phosphorylation was now also increased. Responses to prucalopride per se and the influence thereupon of PDE3 and PDE4 inhibition were similar except that responses were generally smaller. Stimulation of pGC together with PDE4 inhibition increased 5-HT-induced PLB phosphorylation compared to 5-HT alone, consistent with functional responses. sGC stimulation hastened the fade of inotropic responses to 5-HT, while cAMP levels were not altered. PDE3 and PDE4 control the cAMP response to 5-HT4 receptor activation, causing a dampening of downstream signalling. Stimulation of pGC is able to enhance inotropic responses to 5-HT by increasing cAMP levels, while sGC stimulation decreases contraction to 5-HT cAMP independently.
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Affiliation(s)
- Sabine Weninger
- Heymans Institute of Pharmacology, Ghent University, Ghent, 9000, Belgium.
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The development of potential new fluorine-18 labelled radiotracers for imaging the GABAA receptor. Bioorg Med Chem Lett 2013; 23:821-6. [DOI: 10.1016/j.bmcl.2012.11.066] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 11/16/2012] [Accepted: 11/18/2012] [Indexed: 12/13/2022]
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Abstract
Physicians look to biomarkers to inform the management of pulmonary hypertension (PH) at all stages, from assessing susceptibility through screening, diagnosis, and risk stratification to drug selection and monitoring. PH is a heterogeneous disorder and currently there are no accepted blood biomarkers specific to any manifestation of the condition. Brain natriuretic peptide and its N-terminal peptide have been most widely studied. Other candidate prognostic biomarkers in patients with pulmonary arterial hypertension (PAH) include growth and differentiation factor-15, red cell distribution width, uric acid, creatinine, inflammatory markers such as interleukin-6, angiopoietins, and microRNAs. Combining the measurement of biomarkers reflecting different components of the pathology with other modalities may enable better molecular characterisation of PH subtypes and permit improved targeting of therapeutic strategies and disease monitoring.
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Barrier M, Meloche J, Jacob MH, Courboulin A, Provencher S, Bonnet S. Today's and tomorrow's imaging and circulating biomarkers for pulmonary arterial hypertension. Cell Mol Life Sci 2012; 69:2805-31. [PMID: 22446747 PMCID: PMC11115077 DOI: 10.1007/s00018-012-0950-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Revised: 02/18/2012] [Accepted: 02/20/2012] [Indexed: 01/04/2023]
Abstract
The pathobiology of pulmonary arterial hypertension (PAH) involves a remodeling process in distal pulmonary arteries, as well as vasoconstriction and in situ thrombosis, leading to an increase in pulmonary vascular resistance, right heart failure and death. Its etiology may be idiopathic, but PAH is also frequently associated with underlying conditions such as connective tissue diseases. During the past decade, more than welcome novel therapies have been developed and are in development, including those increasingly targeting the remodeling process. These therapeutic options modestly increase the patients' long-term survival, now approaching 60% at 5 years. However, non-invasive tools for confirming PAH diagnosis, and assessing disease severity and response to therapy, are tragically lacking and would help to select the best treatment. After exclusion of other causes of pulmonary hypertension, a final diagnosis still relies on right heart catheterization, an invasive technique which cannot be repeated as often as an optimal follow-up might require. Similarly, other techniques and biomarkers used for assessing disease severity and response to treatment generally lack specificity and have significant limitations. In this review, imaging as well as current and future circulating biomarkers for diagnosis, prognosis, and follow-up are discussed.
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Affiliation(s)
- Marjorie Barrier
- Pulmonary Hypertension Research Group, Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 Chemin Ste-Foy, Québec, QC G1V 4G5 Canada
| | - Jolyane Meloche
- Pulmonary Hypertension Research Group, Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 Chemin Ste-Foy, Québec, QC G1V 4G5 Canada
| | - Maria Helena Jacob
- Pulmonary Hypertension Research Group, Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 Chemin Ste-Foy, Québec, QC G1V 4G5 Canada
| | - Audrey Courboulin
- Pulmonary Hypertension Research Group, Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 Chemin Ste-Foy, Québec, QC G1V 4G5 Canada
| | - Steeve Provencher
- Pulmonary Hypertension Research Group, Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 Chemin Ste-Foy, Québec, QC G1V 4G5 Canada
| | - Sébastien Bonnet
- Pulmonary Hypertension Research Group, Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 Chemin Ste-Foy, Québec, QC G1V 4G5 Canada
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Moran MD, Wilson AA, Elmore CS, Parkes J, Ng A, Sadovski O, Graff A, Daskalakis ZJ, Houle S, Chapdelaine MJ, Vasdev N. Development of new carbon-11 labelled radiotracers for imaging GABAA- and GABAB-benzodiazepine receptors. Bioorg Med Chem 2012; 20:4482-8. [PMID: 22717238 DOI: 10.1016/j.bmc.2012.05.046] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 05/05/2012] [Accepted: 05/12/2012] [Indexed: 11/16/2022]
Abstract
Two quinolines identified as positive allosteric modulators of γ-aminobutyric acid (GABA)(A) receptors containing the α(2) subunit, 9-amino-2-cyclobutyl-5-(6-methoxy-2-methylpyridin-3-yl)-2,3-dihydro-1H-pyrrolo[3,4-b]quinolin-1-one (4) and 9-amino-2-cyclobutyl-5-(2-methoxypyridin-3-yl)-2,3-dihydro-1H-pyrrolo[3,4-b]quinolin-1-one (5), were radiolabelled at the methoxy position with carbon-11 (half-life=20.4 min). These quinolines represent a new class of potential radiotracers for imaging the benzodiazepine site of GABA(A) receptors with positron emission tomography (PET). Both radiotracers were reliably isolated following reaction of their respective pyridinone/pyridinol tautomeric precursors with [(11)C]CH(3)I in clinically useful, formulated quantities (2.9% and 2.7% uncorrected radiochemical yield, respectively, relative to [(11)C]CO(2)) with high specific activities (>70 GBq μ mol(-1); >2 Ci μ mol(-1)) and high radiochemical purities (>95%). The radiosyntheses reported herein represent rare examples of selectively isolating radiolabelled compounds bearing [(11)C]2-methoxypyridine moieties. Although both radiotracers demonstrated promising imaging characteristics based on preliminary ex vivo biodistribution studies in conscious rodents, higher brain uptake was observed with [(11)C]5 and therefore this radiotracer was further evaluated. Carbon-11 labelled 5 readily penetrated the brain (>1 standard uptake value in cortical regions at 15 min post-injection of the radiotracer), had an appropriate regional brain distribution for GABA(A) receptors that appeared to be reversible, and did not show any appreciable radiometabolites in rat brain homogenates up to 15 min post-injection. Preadministration of flumazenil (1, 10 mg kg(-1)) or 5 (5 mg kg(-1)) effectively blocked >50% of [(11)C]5 binding to the GABA(A) receptor-rich regions, thereby suggesting that this radiotracer is worthy of further evaluation for imaging GABA(A) receptors. Additionally (R,S)-N-(1-(3-chloro-4-methoxyphenyl)ethyl)-3,3-diphenylpropan-1-amine, 6, an allosteric modulator of GABA(B) receptors, was efficiently labelled in one step using [(11)C]methyl iodide. Ex vivo biodistribution studies in conscious rats showed low brain uptake, therefore, efforts are underway to discover alternative radiotracers to image GABA(B). In conclusion, [(11)C]5 is worthy of further evaluation in higher species for imaging GABA(A) receptors in the central nervous system.
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Affiliation(s)
- Matthew D Moran
- Centre for Addiction and Mental Health and University of Toronto, 250 College St., Toronto, ON, Canada M5T 1R8
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Study of the regulation of the inotropic response to 5-HT4 receptor activation via phosphodiesterases and its cross-talk with C-type natriuretic peptide in porcine left atrium. Naunyn Schmiedebergs Arch Pharmacol 2012; 385:565-77. [PMID: 22426996 DOI: 10.1007/s00210-012-0746-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 03/01/2012] [Indexed: 10/28/2022]
Abstract
We studied how 5-HT(4) receptor-mediated inotropic responses are regulated at the level of cAMP in porcine left atrium. We used selective phosphodiesterase (PDE) inhibitors to assess which PDE subtypes are responsible for the fade with time of inotropic responses to 5-HT(4) receptor activation with 5-HT and the 5-HT(4) receptor agonist prucalopride. A possible cross-talk via PDEs between cGMP and 5-HT(4) receptor-induced cAMP signalling was evaluated. Electrically paced left atrial pectinate muscles from young male pigs (15-25 kg) were studied in vitro. Simultaneous inhibition of PDE3 plus PDE4 subtypes was necessary to increase the amplitude and completely prevent the fade of the inotropic response to 5-HT and prucalopride. When responses to 5-HT or prucalopride had faded 1 h after addition, the nonspecific PDE-inhibitor IBMX still fully recovered inotropic responses. Stimulation of particulate guanylyl cyclase, together with PDE2 and PDE4 inhibition, delayed the fade of the response to 5-HT, while stimulation of soluble guanylyl cyclase independently of PDEs accelerated the fade of the response to 5-HT. In conclusion, both PDE3 and PDE4 subtypes are responsible for the suppression and the fade of the inotropic response to 5-HT and prucalopride. Signalling through the 5-HT(4) receptor remains fully active for at least 90 min with PDEs continuously regulating the response. cGMP levels, elevated by activation of particulate guanylyl cyclase under PDE2 inhibition, can indirectly enhance 5-HT(4) receptor-mediated signalling, at least when also PDE4 is inhibited, presumably through inhibition of PDE3. Elevation of cGMP generated by soluble guanylyl cyclase attenuates responses to 5-HT independently of PDEs.
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Cumming P, Vasdev N. Molecular Imaging Studies of Second Messenger Pathways: Looking Deeper than the Membrane. MOLECULAR IMAGING IN THE CLINICAL NEUROSCIENCES 2012. [DOI: 10.1007/7657_2012_52] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
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